Handling and presentation of alarms during nuclear plant operation

The problems in presenting alarms for the operators during nuclear power-plant operation are well known. A large number of standing alarms occur during normal operation, and minor plant transients cause a torrent of messages, where new alarms are easily lost. Several approaches, ranging from very sophisticated computer-based systems to relatively simple engineering fixes, have been proposed for the solution of the problem. The potentials for the different methods clearly indicate that no single approach could cope with all the problems, but a good combination of them will improve alarm systems considerably from what is usually accepted today. This article surveys different approaches used in alarm systems and gives some suggestions on how the approaches could be combined into an engineering design. The article is based on both theoretical and experimental work done in Finland in connection with national and international research projects as well as on practical experience from Finnish nuclear power plants.